Configure vertical stacking

We can configure vertical stacking to enable the application placement controller to start more than one instance of the dynamic cluster to improve bottleneck conditions within an application.

• (zos) Vertical stacking is supported on the z/OS operating system, but the WAS for z/OS multiple servant feature is the preferred alternative. Consider using vertical stacking for application servers on the z/OS operating systems only for application servers that host applications that are constrained to run in a single servant application server.

• To use vertical stacking, the nodes in the dynamic cluster must be at the same product version as the deployment manager, or at a later version. Nodes that are at an earlier release than the deployment manager cannot start multiple server instances on the same node.

• Vertical stacking can occur only on nodes that have complete life cycle management. We cannot configure vertical stacking for dynamic clusters that have manually defined cluster members.

Use vertical stacking to improve bottleneck conditions in the application. With vertical stacking, multiple server instances can start on a node. By configuring multiple server instances, we can use all the power that is available on the nodes when a large workload exists for the application.

1. Determine whether the application has an internal bottleneck by profiling the application. The application placement controller assumes that the only resource bottleneck that an application might have is either in the processor or in memory. Otherwise, the application might have an internal bottleneck.

   1. Run an instance of the application on each node.

   2. Increase the load for the application.

   3. Analyze the runtime reports, the throughput curves and processor utilization charts for the nodes that are running the application. Click Runtime operation > Reports.
   If the throughput curve saturates while increasing the load, but the processor utilization remains well under 100%, the application might have an internal bottleneck. Configure vertical stacking to improve these bottleneck conditions. If the server instances are able to reach processor utilization near 100%, do not enable vertical stacking.

2. Determine the appropriate stacking number. The stacking number is the number of application servers for a cluster that are needed to use all the power of a node. For more information about determining a stacking number, read about determining the stacking number for a dynamic cluster.

3. Enable vertical stacking and the stacking number. If wer dynamic cluster is deployed to a node group that has homogeneous nodes, we can configure the stacking number one time in the console. If the dynamic cluster is deployed to a node group that has heterogeneous nodes, configure the stacking number by specifying custom properties.

   • For more information about enabling vertical stacking for a dynamic cluster that is on homogenous nodes, read about configuring a dynamic cluster with homogeneous nodes to support vertical stacking.

   • For more information about enabling vertical stacking for a dynamic cluster that is on heterogeneous nodes, read about configuring a dynamic cluster with heterogeneous nodes to support vertical stacking.

Results

When a large workload exists, the application placement controller can fully use the power of the nodes by starting multiple cluster instances on each node.

The general formula to determine the percentage of the processor used by each instance on a node is 100%/maximum_number_of_stacked_instances. For example, if three instances are stacked, then workload is throttled to prevent any one of these instances from using more than 33% of the processor.

What to do next

Tune and monitor the application placement configuration.

Subtopics

• (dist)(zos) Determine the stacking number for a dynamic cluster
  We can use profiling to determine the stacking number for the dynamic cluster. The stacking number is the number of cluster instances that are needed to use all the power of a node.

• (dist)(zos) Configure a dynamic cluster with homogeneous nodes to support vertical stacking
  We can configure vertical stacking for a dynamic cluster with nodes that have similar computing power by updating settings in the console.

• (dist)(zos) Configure a dynamic cluster with heterogeneous nodes to support vertical stacking
  We can configure vertical stacking for a dynamic cluster with nodes that each have different computing power by configuring custom properties for each node.

Related concepts

Dynamic clusters

Related tasks

Monitor and tune the application placement controller

Determine the stacking number for a dynamic cluster

Configure a dynamic cluster with homogeneous nodes to support vertical stacking

Configure a dynamic cluster with heterogeneous nodes to support vertical stacking

Create dynamic clusters

Deploy enterprise applications

Intelligent Management: static clusters versus dynamic clusters

Related information:

Intelligent Management: application placement custom properties